The invention relates to a method of manufacturing rotationally symmetrical glass bodies. In the method, the starting material for the glass body is a thixotropic suspension consisting of powdered glass in a liquid dispersing agent. The suspension is introduced into a hollow mold whose geometry corresponds to that of the glass body to be formed. The hollow mold is rotated about its longitudinal axis to deposit the suspension on the inner wall of the hollow mold. The green body thus formed is then purified and sintered.
The invention further relates to an apparatus for performing such a method, and to the use of the glass bodies manufactured by the method according to the invention.
The method described above is particularly suitable for the manufacture of performs for optical waveguides made of quartz glass.
Optical waveguides have a wide range of application. They are used, for example, in short-distance light-transmission arrangements or long-distance light-transmission arrangements as used in optical communication systems. They predominantly consist of a type of glass which has a high silicon dioxide content (which, if necessary, contains a dopant to adjust the refractive index of the glass).
Types of glass which can suitably be used for optical waveguides, can also advantageously be used for the manufacture of lamp envelopes for halogen lamps or gas-discharge lamps. This is because these types of glass must, like the types used for optical waveguides, be substantially anhydrous and contain a high silicon dioxide content.
The British patent GB No. 682580 describes a method of manufacturing porous glass tubes, for example for use as filters in laboratories, by a centrifuging process. In this method, it is important to obtain a highly uniform distribution and size of the pores in the sintered body containing glass particles and to ensure that the pores are in communication with one another. For this purpose, the suspension consists of powered glass having a highly uniform grain size. The glass powder is mixed, during constant stirring, with a binder, for example an aqueous glycerine solution, which presents settling of the solid particles. The powder is also mixed with wetting agents and agents which inhibit foaming of the suspension, in order to obtain a distribution of the solid particles in the suspension in conformity with the desired porosity.
Such a method is unsuitable when the solid particles to be deposited on the inner wall of a centrifuge must be as densely spaced as possible, and when the suspensions contain solid particles of very different particle sizes.